1. Field of the Invention
This invention relates to the field of wellbore fluids and more specifically to the field of wellbore fluids comprising a resilient material as well as methods for using such wellbore fluids to service a wellbore.
2. Background of the Invention
A natural resource such as oil or gas residing in a subterranean formation can be recovered by drilling a well into the formation. The subterranean formation is usually isolated from other formations using a technique known as well cementing. In particular, a wellbore is typically drilled down to the subterranean formation while circulating a drilling fluid through the wellbore. After the drilling is terminated, a string of pipe, e.g., casing, is run in the wellbore. Primary cementing is then usually performed whereby a cement slurry is pumped down through the string of pipe and into the annulus between the string of pipe and the walls of the wellbore to allow the cement slurry to set into an impermeable cement column and thereby seal the annulus. Secondary cementing operations may also be performed after the primary cementing operation. One example of a secondary cementing operation is squeeze cementing whereby a cement slurry is forced under pressure to areas of lost integrity in the annulus to seal off those areas.
After completion of the cementing operations, production of the oil or gas may commence. The oil and gas are produced at the surface after flowing through the wellbore. As the oil and gas pass through the wellbore, heat may be passed from such fluids through the casing and into the annular space, which typically results in expansion of any fluids in the annular space. Such an expansion may cause an increase in pressure within the annular space, which is known as annular pressure buildup. Annular pressure buildup typically occurs when the annular volume is fixed. For instance, the annular space may be closed (e.g., trapped). The annular space is trapped to isolate fluids within the annulus from areas outside the annulus. Trapping of an annular space typically occurs near the end of cementing operations after well completion fluids such as spacer fluids and cements are in place. The annular space is conventionally trapped by closing a valve, energizing a seal, and the like. Trapping presents operational problems. For instance, annular pressure buildup may cause damage to the wellbore such as damage to the cement sheath, the casing, tubulars, and other equipment.
To prevent such damage by annular pressure buildup, pressure relieving/reducing methods have been developed such as using syntactic foam wrapping on the casing, placing nitrified spacer fluids above the cement in the annulus, placing rupture disks in an outer casing string, designing “shortfalls” in the primary cementing operations such as designing the top of the cement column in an annulus to be short of the previous casing shoe, using hollow spheres, and others. However, such methods have drawbacks. For instance, the syntactic foam may cause flow restrictions during primary cementing of the casing within the wellbore. In addition, the syntactic foam may detach from the casing and/or become damaged as the casing is installed. Drawbacks with placing the nitrified spacer fluids include logistical difficulties (e.g., limited room for the accompanying surface equipment), pressure limitations on the wellbore, and the typical high expenses related thereto. Further drawbacks with placing the nitrified spacer fluids include loss of returns when circulating the nitrified spacer into place and in situations wherein the geographic conditions provide difficulties in supplying the proper equipment for pumping the nitrified spacer. Additional drawbacks include the rupture disks so comprising the casing string after failure of the disks that continuing wellbore operations may not be able to proceed. Further drawbacks include the designed “shortfall,” which may not occur due to wellbore fluids not being displaced as designed and cement channeling up to a casing shoe and trapping it. Moreover, problems with the hollow spheres include the spheres failing before placement in the annulus.
Consequently, there is a need for reducing annular pressure buildup. In addition, there is a need for an improved manner for addressing the problems of annular pressure buildup.